Updated August 20th, 2016.
Buttercups come from the genus Ranunculus which includes 600 species of plants.
They are a well known wild plant that usually flowers in the spring,
However its flowers may be found throughout the summer before dying off in the fall.
Buttercups are renown for having petals that are often highly lustrous, especially in its yellow species.
Some species are popular ornamental flowers in horticulture, with many cultivars selected for large and brightly colored flowers.(source)
So can hamsters eat buttercups?
Buttercups in themselves are fine in themselves for them to eat.
However, it is not a good idea to feed grasses from the outside as they may contain parasites or parasites.
So buttercups are a food to avoid as far as hamsters are concerned.